Oligodendroglioma: HMB-45 positivity using catalyzed signal amplification method: an immunohistochemical (HMB-45, CD31, p53, Mib-1) and ultrastructural study.

Although melanin synthesis and the presence of melanosomes are exceptionally reported in nervous system tumors, there is no record of melanotic oligodendrogliomas in the literature. The purpose of the current study was to evaluate whether melanosomes are immunohistochemically and ultrastructurally detectable in nonmelanotic oligodendrogliomas and to verify whether these data are related to prognosis. Thirty surgical specimens (19 primary lesions and 11 recurrences) from 19 patients were examined. Median survival was 80 months. Immunohistochemical studies were performed using the monoclonal antibodies HMB-45, CD31. Mib-1, and p53. Using catalyzed signal amplification (CSA), HMB-45 positivity was noticed in 3 (10%) of the oligodendrogliomas being studied. No correlation with survival was found. Ultrastructural examination displayed the presence of melanosomelike structures. Tumor vascularization, estimated by means of CD31 antibody, was increased in 6 of 19 primary lesions but there was no significant correlation with survival. Nine of the19 primary lesions were p53 negative. In these cases, survival was longer than in p53-positive tumors (P = 0.0213). Proliferation rate, evaluated with Mib-1, was unrelated to survival, but proved greater in recurrences (10 of 11 cases) than in primary tumors (7 of 19 lesions; P = 0.007).